Disclosed herein are reactive ink components and methods for forming images using the reactive inks.
Ink jetting devices are known in the art, and thus extensive description of such devices is not required herein. As described in U.S. Pat. No. 6,547,380, which is hereby incorporated by reference herein in its entirety, ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field that adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium.
There are at least three types of drop-on-demand ink jet systems. One type of drop-on-demand system is a piezoelectric device that has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. Another type of drop-on-demand system is known as acoustic ink printing wherein an acoustic beam exerts a radiation pressure against objects upon which it impinges. Thus, when an acoustic beam impinges on a free surface such as at the liquid/air interface of a pool of liquid from beneath, the radiation pressure which it exerts against the surface of the pool may reach a sufficiently high level to release individual droplets of liquid from the pool, despite the restraining force of surface tension. Focusing the beam on or near the surface of the pool intensifies the radiation pressure it exerts for a given amount of input power. Still another type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets. The major components of this type of drop-on-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink vehicle (usually water) in the immediate vicinity to vaporize almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands.
In a typical design of a piezoelectric ink jet device utilizing phase change inks printing directly on a substrate or on an intermediate transfer member, such as the one described in U.S. Pat. No. 5,372,852, which is hereby incorporated by reference herein in its entirety, the image is applied by jetting appropriately colored inks during four to eighteen rotations (incremental movements) of a substrate (an image receiving member or intermediate transfer member) with respect to the ink jetting head, i.e., there is a small translation of the print head with respect to the substrate in between each rotation. This approach simplifies the print head design, and the small movements ensure good droplet registration. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops.
Thermal ink jet processes are well known and are described, for example, in U.S. Pat. Nos. 4,601,777, 4,251,824, 4,410,899, 4,412,224 and 4,532,530, the disclosures of each of which are hereby totally incorporated herein.
Ink jet printing processes may employ inks that are solid at room temperature and liquid at elevated temperatures. Such inks may be referred to as hot melt inks or phase change inks. For example, U.S. Pat. No. 4,490,731, which is hereby incorporated by reference herein in its entirety, discloses an apparatus for dispensing solid ink for printing on a substrate such as paper. In thermal ink jet printing processes employing hot melt inks, the solid ink is melted by the heater in the printing apparatus and utilized (i.e., jetted) as a liquid in a manner similar to that of conventional thermal ink jet printing. Upon contact with the printing substrate, the molten ink solidifies rapidly, enabling the colorant to substantially remain on the surface of the substrate instead of being carried into the substrate (for example, paper) by capillary action, thereby enabling higher print density than is generally obtained with liquid inks. Advantages of a phase change ink in ink jet printing are thus elimination of potential spillage of the ink during handling, a wide range of print density and quality, minimal paper cockle or distortion, and enablement of indefinite periods of nonprinting without the danger of nozzle clogging, even without capping the nozzles.
Xerographic and ink jet print image permanence can be affected negatively in the office environment such as by common water spills, fingerprints, heat and abrasion. In order to improve print image permanence, a coating is often applied over the print. Such overcoats can be solvent or aqueous based and curable or non-curable. Curable inks have been developed to provide robust images with improved image permanence. Ultra-violet curable inks and overcoats have been developed to form extremely robust images. With this type of ink technology, the printed ink itself can be made tougher by cross-linking the ink on and optionally within the substrate (such as paper).
U.S. Pat. Nos. 7,276,614 and 7,259,275, which are each hereby totally incorporated by reference herein in their entireties, disclose ultraviolet curable compounds that are soluble in phase change ink carriers and can be incorporated into the phase change ink without adversely affecting the viscosity characteristics of the ink at desired jetting temperatures.
U.S. Patent Publication Number 20080000384, which is hereby incorporated by reference herein in its entirety, discloses a radiation curable phase change ink comprising an ink vehicle that includes at least one curable carrier, at least one gellant, at least one curable wax, and at least one photoinitiator. In a method of forming an image with the ink, the radiation curable phase change ink is melted, then jetted onto an image receiving substrate, wherein the radiation curable phase change ink forms a gel state, exposed to ultraviolet light to cure the curable components of the radiation curable phase change ink. The wax cures into the structure of the ink, thereby generating a robust image of excellent gloss.
For both curable inks and overcoats, cross-linking of the resin can be achieved by ultraviolet irradiation. However, ultra-violet curable materials can require complex and expensive ultra-violet light curing stations or expensive photoinitiators to cure or fix the images onto a substrate. Other inks, such as electron beam curable inks, can also require expensive curing stations and shielding devices.
Two part reactive cross-linking formulations based on free radical polymerization are known. However, none of these chemistries have achieved cross-linking times on the order of seconds. Artisans, one example being those who work with dental resin applications, prefer formulations that can be easily mixed and that permit some forming time prior to full cure. Fast curing formulations have not been desirable and therefore have not been developed.
U.S. Patent Publication Number 20080295731, which is hereby incorporated by reference herein in its entirety, describes a reactive ink set including three mixtures of radically polymerizable monomers. The ink set includes a first mixture including a peroxide, a second mixture including a peroxide decomposition agent, and an optional third mixture that does not include a peroxide or a peroxide decomposition agent. The first mixture and the second mixture polymerize to form a solid ink on the substrate following jetting in the liquid state.
U.S. Pat. No. 5,354,840, which is hereby incorporated by reference herein in its entirety, discloses functional-amine polyesters having at least a first residue of a first monomer, a second residue of a second monomer, and from about 0.1 to about 3.0 mole percent of a functional-amine residue of a functional amine prepared by reacting the first and second monomers and the functional amine in an inert atmosphere. The functional amine has a functional group which facilitates polymerizing the amine and the first and second monomers. The amine residue facilitates reaction of the functional-amine polyester in an organic peroxide cross-linking reaction system.
U.S. Pat. Nos. 5,380,769, 5,645,888, and 5,958,169, which are hereby incorporated by reference herein in their entireties, disclose reactive ink compositions that utilize at least two reactive components, a base ink component and a curing component, that are applied to a receiving substrate separately. The base ink component includes an ink carrier, a compatible colorant, and a cross-linkable constituent, and the curing component is a cross-linking agent. Upon exposure of the base ink component to the curing component, at least a portion of the ink is cross-linked to provide a printed image that is durable and abrasion-resistant
U.S. Pat. No. 6,114,076, which is hereby incorporated by reference herein in its entirety, discloses a reactive melt mixing process for the preparation of a low fix temperature toner resin. The process includes (a) mixing a reactive base resin, an initiator, and a polyester with amine functionality, and (b) crosslinking the resulting polymer melt under high shear to form a crosslinked toner resin.
While these technologies are suitable for their intended purposes, there remains a need in large scale production and home and office printing for an improved ink system that can provide robust, scratch, and mar resistant images that are inexpensive and efficiently produced. Further, there is a need for fast curing reactive inks that can be reliably used with desired print speeds.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.